Mobile storage device

ABSTRACT

Disclosed is a mobile storage device that combines high storage capacity and performance with low power consumption and portable operation. The key enabling component of the mobile storage device is an integrated base ceramic substrate upon which a plurality of spiral conductors, magnetoresistive sensors and interconnect conductors have been fabricated by a semiconductor process, and upon which electronic integrated circuits have been assembled. A dual-rotor spindle assembly, a multi-arm actuator assembly and a ceramic housing are assembled with the integrated base forming a chamber that is hermetically sealed and can been pressured with a low viscosity gas at below ambient pressures.

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] This invention uses the transmission of my co-pendingapplications, Ser. No. 09/827,119, filed Apr. 5, 2001, and entitled“Dual-Modular Actuators Having a Common Axis of Rotation” andapplication, Ser. No. 09/932,684, filed Aug. 20, 2001 and entitled“Variable Speed Integrated Planer Motor Assembly”.

BACKGROUND

[0002] 1. Field of Invention

[0003] This invention relates to Data Storage Systems, specificallythose using magnetic recording on rigid disks.

[0004] 2. Description of Prior Art

[0005] Hard Disk Drives (HDDs) are based on magnetic recordingtechnology which has been increasing the amount of data stored on asingle 2.5-inch disk from today's 40 GB to an expected 180 GB in two tofour years. However the manufacturing of HDDs has not kept pace withthese advances and remains, for the most part, a labor intensiveassembly operation. This approach requires expensive tooling andspecialized capital equipment expenditures each time a new product isintroduced. In addition, high power consumption and high performance aresynonymous with HDDs and limits their use in emerging applicationsrequiring mobile high speed digital storage and playback. One of themajor contributors, to high power consumption, is the viscous drag ofthe surrounding air on the magnetic disks during high speed angularrotation. This drag is directly proportional to the air density and itsviscosity which surrounds the disks and leads to high temperatureswithin the HDD. In addition, the surrounding air can be humid andcondensation can occur on the surface of the disks during operation.

OBJECTS AND ADVANTAGES

[0006] Advances in disk storage capacities coupled with the high I/Operformance of multi-actuators and high rotational speed disk drives,has created an opportunity to provide these features in a Mobile StorageDevice (MSD) that can be either battery or bus powered. Accordingly,several objects and advantages of my invention are:

[0007] to provide a Mobile Storage Device that is battery and buspowered.

[0008] to provide an Integrated Base that integrates all key electricalcomponents on a high strength ceramic substrate witch was manufacturedby processes and equipment common to the semiconductor industry.

[0009] to provide a Mobile Storage Device totally enclosed in ahermetically sealed chamber.

[0010] to provide a robust Mobile Storage Device that can rotate at highrotational speeds with low power consumption.

[0011] to provide a Mobile Storage Device with multiple low inertiaActuator Arms for fast access times with minimum power.

[0012] to provide a variable speed Spindle Motor

[0013] Further objects and advantages of my invention will becomeapparent from a consideration of the drawings and ensuing description.

DRAWING FIGURES

[0014]FIG. 1a-1 c shows front, profile and back views of the IntegratedBase, 100.

[0015]FIG. 2a-2 c shows the top, front, and bottom views of the disk,rotor and spindle assemblies.

[0016]FIG. 3a shows the top, front, and bottom views of the IntegratedArm and FIG. 3b shows the top and front views of the multi-gap ActuatorAssembly.

[0017]FIG. 4 shows the top, front and profile views of the Housing.

[0018]FIG. 5a-5 b shows the top and front view of the components andassemblies of the Mobile Storage Device.

[0019]FIG. 6 is various views of the Mobile Storage Device with theLithium Polymer Battery and cable assembled.

[0020]FIG. 7a-7 c is cross sectional views of two, three and four armMobile Storage Devices.

[0021]FIG. 8a-8 c shows the relationship between the permanent magnets,stator coils and biased Mr Sensors and the resulting electricalwaveforms.

DESCRIPTION—FIGS. 1 to 7

[0022] Integrated Base 100

[0023]FIG. 1a-1 c shows the front, profile and back views of theIntegrated Base (IB), 100, a key and enabling component of the MobileStorage Device. The IB consists of two parts; a bottom 10 and a top 20and was manufactured on ceramic substrate 5 using the followingmaterials and processes.

[0024] 1: In the preferred embodiment, ceramic substrate 5 ismanufactured with an Yttria-partially Stabilized Zirconia (YTZP)material whose salient properties are given in Table 1. This materialexhibits excellent strength and fracture toughness and is able to absorbthe high energy of impact without shattering or deforming. TABLE 1Yttria-Partially Stabilized Zirconia (YTZP)¹ Density: 6.02 (grams/cm3)Flexural Strength 1,300 (MPa) Fracture Toughness 13 (MPa*m^(1/2))Compressive Strength 2,500 (MPa) Coefficient of Linear Expansion 10.3(10⁻⁶/° C.) Thermal Conductivity 2.2 (W/m*K)

[0025] 1-As per CoorsTek, a manufacturer of Technical Ceramics

[0026] 2: Front to back via holes are laser machined in substrate 5 andfilled with low resistivity copper. The substrate is now lapped andpolished, on both surfaces, for flatness and smoothness.

[0027] 3: IC interconnect traces 15, stator coil 21 and Mr Stripes 22interconnects 26, and stator coils 11 and Mr Stripes 12 interconnects 16are fabricated by sputtering 2-4 microns of copper on the front and backsurfaces of substrate 5. Photoresist is applied to both surfaces,exposed with photo masks defining the interconnect traces 15, 26 and 16,and developed. The substrate is sputter etched, or ion milled, to removeall copper not covered with photoresist.

[0028] 4: The biased Mr elements, 12 and 22, are fabricated bysputtering a magneto resistive material, such as 80-20 Nickel-Iron(Ni—Fe), followed by a film of Copper (Cu). Photoresist is applied,exposed, and developed and then the substrate is sputter etched, or ionmilled, to removing the copper-Ni—Fe material not covered withphotoresist.

[0029] 5: A 5-6 micron film of aluminum oxide (Al²O³) is sputterdeposited on both surfaces of substrate 5 and then double sided lappedand polished with a process know as CMP (Chemical MechanicalPlanarization).

[0030] 6: Via's back to interconnect traces 15, 16 and 26 are fabricatedby applying photoresist to both surfaces of substrate 5, expose todefine via location, develop, and etch Al²O^(3.)

[0031] 7: The fabrication of the spindle motor stator coils 11 and 21starts with the sputtering of a copper seed layer followed by theapplication of an ultra-thick photoresist (20-100 microns) on the frontsurface of substrate 5. The substrate is exposed with a photo maskdefining the spiral coil pattern, developed, and copper is electroplatedinto the openings with the thickness of the copper equal to thephotoresist thickness. The photoresist is stripped and the copper seedlayer is removed by etching. These resists, such as the Shipley BRP100or the Clariant AZ PLP 100XT, can achieve aspect ratios of 10 to 1(height/width) with near vertical walls and optimized for thefabrication of copper electroplated conductors.

[0032] 8: Mount “bumped” IC's 70, 71 and 72 and the mini-connector 75using a solder re-flow operation.

[0033] 9: An YTPZ Zirconia spindle motor shaft 77 is bonded to substrate5 in a fixture to ensure its extension and perpendicularity to substrate5.

[0034] 10: A precision ceramic washer, 92, and a spring type washer 91are bonded to substrate 5 as shown in FIGS. 1a and 1 b. Washer 92establishes the spindle motor air gap and washer 91 will pre-load thespindle motor bearings.

[0035] Dual Rotor Spindle Assembly 200

[0036]FIG. 2a is the top, front and bottom views of the Magnetic Disk,210, consisting of a magnetic film deposited on a glass substrate.Magnetic Disk 210 is available from a variety of manufactures in highvolume and at reasonable cost.

[0037]FIG. 2b is the top, front and bottom view of the top 215 andbottom 216 rotor assemblies consisting of thin cylindrical permanentmagnets of Neodymium-Iron-Boron (NdFeB) 211 mounted on rings 212 of50-50 Nickel-Iron (Ni—Fe), a soft magnetic material having highsaturation magnetization. The Ni—Fe ring acts as a rigid holder of theNdFeB permanent magnet, and a low reluctance magnetic flux return. Therotor assemblies are ground and lapped flat and then magnetizedperpendicular to their face.

[0038]FIG. 2c is the top, front and bottom view of the assembled SpindleAssembly 200. It was assembled as follows:

[0039] Bearing Sleeve 250 consists of two precision bearings installedin an alumina (Al₂O₃) ceramic sleeve. The bearings were installed withtheir races flush with the ends of the ceramic sleeve.

[0040] Magnetic recording disks 210 are precisely located and bonded tobearing sleeve 250, using pre-forms of UW curable glass filledadhesives.

[0041] Rotor Assemblies 215 and 216 are located and bonded to magneticdisks 210.

[0042] Actuator Assembly 300

[0043]FIG. 3a is the top, front and bottom view of the Integrated ArmAssembly 305.

[0044]FIG. 3b is the top and front view of the Actuator Assembly 300consisting of two Integrated Arms 305 mounted to multi-gap Voice CoilMotor 310 using precision spacers 311.

[0045] Housing 400

[0046]FIG. 4 shows the top, front and profile view of the injectionmolded YTPZ Zirconia ceramic Housing, 400. The top and bottom surfaceshave been ground and polished parallel and flat and are separated by adimension controlled to within 0.0001 inches.

[0047] Assembly of the Mobile Storage Device 500

[0048]FIG. 5a is the top view and FIG. 5b is the front view of theassemblies and components, of the Mobile Storage Device 500, which canbe assembled as follows.

[0049] Dual-Rotor Spindle Assembly 200 is assembled to bottom IntegratedBase 10 over the spindle motor shaft 77 with the inner race of thespindle motors bearings resting on precision spacer 92.

[0050] Actuator assembly 300 is placed in position on the bottomIntegrated Base 10 and secured with an UW curable epoxy adhesive.

[0051] Housing 400 is bonded to bottom Integrated Base 10 with acontinuous film so as to form an air-tight seal.

[0052] The top Integrated Base 20 is now bonded to Housing 400 with acontinuous film so as to form an air-tight seal.

[0053] The chamber formed by the top Integrated Base 20, the bottomIntegrated Base 10 and the Housing 400 can now be evacuated and refilledwith a low viscosity gas at a pressure below one atmosphere.

[0054] Mobile Storage Device 500

[0055]FIG. 6 shows the attachment of the Lithium Polymer battery 625 anda electrical cable connecting interconnects 26 to the motor control ICon the bottom Integrated Base 10.

[0056] Multi-Integrated Arm Mobile Storage Devices

[0057]FIG. 7a-7 c shows the side view of a two, three and fourIntegrated Arms Actuator Assemblies and the addition of magnetic disks210 to spindle assembly 200. The Integrated Arms can be operatedindependently or can be mechanically secured together and operated as asingle unit.

OPERATION—FIG. 8

[0058] The NdFeB magnets 211 have been magnetized, perpendicular totheir faces, into 6 equal segments of alternating polarity as shown inFIG. 8a. This creates a magnetic intensity in the air gap of +B and −B.With the Mr Sensors biased to the magnetic intensity −B, the resistanceof the Mr Stripe will change when the magnetic intensity in the air gapis +B, and the resistance will remain the same when the magneticintensity in the air gap is −B.

[0059] The relationship between the spiral stator coils 11, Mr Sensors12 and NdFeB magnet 211 is shown in FIG. 8b. The start of the statorcoil 11 is labeled S1 and the spiral conductor goes along radial linesinward in region 1 and along radial lines outward in region 2. Region 1is connected to region 2 along circular arc conductors until itterminates in the center of the spiral coil. In the preferredembodiment, the angular widths of regions 1 and 2 are 30° and they areseparated by an angular width of 30°. A mirror image of this spiral coilis located as shown in FIG. 8b and the following table. Spiral Coil 1Spiral Coil 2 Start End Start End Region 1  0 30 240 270 Region 2 60 90180 210

[0060] A duplicate of spiral stator coil 11 and Mr Stripes 12 are madeon the top Integrated Base 20. The top NdFeB magnet is offset 30° fromthe bottom magnet as shown in FIG. 8b.

[0061] The first Mr Sensor is located 120° from the start conductor inregion 1 and the second Mr Sensor is located 30° from the first. Whenthe bottom NdFeB magnet rotates CCW relative to spiral stator coil 11,the outputs of the Mr Stripes, labeled Mr1 and Mr2, will be as shown inthe bottom waveforms of FIG. 8c with the outputs reflecting the polarityand intensity of the magnetic field in the air gap. The logical signalsMr1 and Mr2 are used to derive the current gating waveforms I+ and I−.During I+, a positive current from S1 to S2 produces a positive torqueand during I−, a negative current produces a positive torque.

[0062] With the top NdFeB magnet offset by 30° from the bottom magnet,the top waveforms will be identical to the bottom waveforms but offsetby 30°.

[0063] The combined I+ and I− waveforms, from the bottom and top MrSensors, allow current, and therefore torque, to be applied to thestator coils on a near continuous basis.

CONCLUSIONS, RAMIFICATIONS, AND SCOPE

[0064] Accordingly, the reader will see that the Mobile Storage Deviceof this invention, has shown and demonstrated;

[0065] a Mobile Storage Device having high performance and capacity withlow power consumption.

[0066] a Mobile Storage Device which is battery and bus powered

[0067] a Mobile Storage Device where the key and enabling components aremanufactured using processes and equipment common to the semiconductorindustry.

[0068] a variable speed dual-rotor spindle motor with near continuoustorque control.

[0069] a Mobile Storage Device with multiple actuator arms and disks.

[0070] A Mobile Storage Device with the actuator and spindle assembliesenclosed in a hermetically sealed chamber with the electronics.

[0071] While my above description contains many specifications, theseshould not be construed as limitations on the scope of the invention,but rather as an exemplification of one preferred embodiment thereofMany other variations are possible. For example the Integrated Basecould be made from other materials, use other semiconductor processes,have other electrical components and have different shapes and sizes.Accordingly, the scope of the invention should be determined not by theembodiments illustrated, but by the appended claims and their legalequivalents.

I claim:
 1. A mobile storage device comprising: a top and bottomintegrated base including a thin ceramic substrate having a plurality ofspiral conductor patterns, a plurality of magnetoresistive sensors, anda conductor interconnect pattern for IC, connector and flex cableattachment; a shaft; a spindle assembly wherein each spindle assembly ismounted to and rotates about said shaft and each spindle assemblyincludes a least one magnetic disk and at least one permanent magnetrotor and said magnetic disks and said permanent magnets are assembledin combination with a ceramic bearing sleeve; an actuator assembly; aceramic housing; wherein the top and bottom integrated base assembliesare assembled and bonded to said ceramic housing forming a hermeticallysealed chamber containing the spindle and actuator assemblies; whereinsaid permanent magnets interact with said spiral conductor patterns toprovide torque to the spindle assembly.